diff --git a/core/api/src/main/java/org/onosproject/net/flow/criteria/UnresolvedExtensionSelector.java b/core/api/src/main/java/org/onosproject/net/flow/criteria/UnresolvedExtensionSelector.java
index 17f527b..22bf95c 100644
--- a/core/api/src/main/java/org/onosproject/net/flow/criteria/UnresolvedExtensionSelector.java
+++ b/core/api/src/main/java/org/onosproject/net/flow/criteria/UnresolvedExtensionSelector.java
@@ -17,7 +17,6 @@
 
 import org.onosproject.net.flow.AbstractExtension;
 import java.util.Arrays;
-import java.util.Objects;
 import static com.google.common.base.MoreObjects.toStringHelper;
 
 
@@ -57,7 +56,7 @@
 
     @Override
     public int hashCode() {
-        return Objects.hash(bytes);
+        return Arrays.hashCode(bytes);
     }
 
     @Override
diff --git a/core/api/src/main/java/org/onosproject/net/flow/instructions/Instructions.java b/core/api/src/main/java/org/onosproject/net/flow/instructions/Instructions.java
index 9bd7df5..33b7482 100644
--- a/core/api/src/main/java/org/onosproject/net/flow/instructions/Instructions.java
+++ b/core/api/src/main/java/org/onosproject/net/flow/instructions/Instructions.java
@@ -101,7 +101,6 @@
      * @return set-queue instruction
      */
     public static SetQueueInstruction setQueue(final long queueId, final PortNumber port) {
-        checkNotNull(queueId, "queue ID cannot be null");
         return new SetQueueInstruction(queueId, port);
     }
 
@@ -328,7 +327,6 @@
      * @return a l3 modification
      */
     public static L3ModificationInstruction modL3ArpOp(short op) {
-        checkNotNull(op, "Arp operation cannot be null");
         return new ModArpOpInstruction(L3SubType.ARP_OP, op);
     }
 
@@ -428,7 +426,6 @@
      * @return a L2 modification
      */
     public static L2ModificationInstruction modTunnelId(long tunnelId) {
-        checkNotNull(tunnelId, "Tunnel id cannot be null");
         return new L2ModificationInstruction.ModTunnelIdInstruction(tunnelId);
     }
 
diff --git a/core/api/src/main/java/org/onosproject/net/flow/instructions/UnresolvedExtensionTreatment.java b/core/api/src/main/java/org/onosproject/net/flow/instructions/UnresolvedExtensionTreatment.java
index bbe1d33..6c4a8c2 100644
--- a/core/api/src/main/java/org/onosproject/net/flow/instructions/UnresolvedExtensionTreatment.java
+++ b/core/api/src/main/java/org/onosproject/net/flow/instructions/UnresolvedExtensionTreatment.java
@@ -19,7 +19,6 @@
 import com.google.common.base.MoreObjects;
 import org.onosproject.net.flow.AbstractExtension;
 import java.util.Arrays;
-import java.util.Objects;
 
 /**
  * Unresolved extension treatment.
@@ -57,7 +56,7 @@
 
     @Override
     public int hashCode() {
-        return Objects.hash(bytes);
+        return Arrays.hashCode(bytes);
     }
 
     @Override
diff --git a/core/api/src/main/java/org/onosproject/net/intent/IntentOperationContext.java b/core/api/src/main/java/org/onosproject/net/intent/IntentOperationContext.java
index 6fc3f2e..528f4ba 100644
--- a/core/api/src/main/java/org/onosproject/net/intent/IntentOperationContext.java
+++ b/core/api/src/main/java/org/onosproject/net/intent/IntentOperationContext.java
@@ -103,7 +103,7 @@
         IntentOperationContext that = (IntentOperationContext) obj;
         return Objects.equals(intentsToInstall, that.intentsToInstall) &&
                 Objects.equals(intentsToUninstall, that.intentsToUninstall) &&
-                Objects.equals(intentInstallationContext, intentInstallationContext);
+                Objects.equals(intentInstallationContext, that.intentInstallationContext);
     }
 
     @Override
diff --git a/core/api/src/main/java/org/onosproject/store/cluster/messaging/ClusterMessage.java b/core/api/src/main/java/org/onosproject/store/cluster/messaging/ClusterMessage.java
index 4c03699..5327d48 100644
--- a/core/api/src/main/java/org/onosproject/store/cluster/messaging/ClusterMessage.java
+++ b/core/api/src/main/java/org/onosproject/store/cluster/messaging/ClusterMessage.java
@@ -155,6 +155,6 @@
 
     @Override
     public int hashCode() {
-        return Objects.hash(sender, subject, payload);
+        return Objects.hash(sender, subject, Arrays.hashCode(payload));
     }
 }
diff --git a/core/api/src/test/java/org/onosproject/net/link/LinkProviderRegistryAdapter.java b/core/api/src/test/java/org/onosproject/net/link/LinkProviderRegistryAdapter.java
index d2cfec2..c0ee902 100644
--- a/core/api/src/test/java/org/onosproject/net/link/LinkProviderRegistryAdapter.java
+++ b/core/api/src/test/java/org/onosproject/net/link/LinkProviderRegistryAdapter.java
@@ -36,11 +36,18 @@
 
     @Override
     public void unregister(LinkProvider provider) {
+        if (providerService != null && provider.id().equals(providerService.provider().id())) {
+            providerService = null;
+        }
     }
 
     @Override
     public Set<ProviderId> getProviders() {
-        return ImmutableSet.of(providerService.provider().id());
+        if (providerService != null) {
+            return ImmutableSet.of(providerService.provider().id());
+        } else {
+            return ImmutableSet.of();
+        }
     }
 
     public LinkProviderServiceAdapter registeredProvider() {
diff --git a/core/api/src/test/java/org/onosproject/security/PermissionTest.java b/core/api/src/test/java/org/onosproject/security/PermissionTest.java
index 191d868..bdab240 100644
--- a/core/api/src/test/java/org/onosproject/security/PermissionTest.java
+++ b/core/api/src/test/java/org/onosproject/security/PermissionTest.java
@@ -17,8 +17,6 @@
 package org.onosproject.security;
 
 import static org.junit.Assert.assertEquals;
-import static org.junit.Assert.assertSame;
-
 import org.junit.Test;
 
 /**
@@ -70,7 +68,7 @@
     public void testEqualsObject() {
         Permission permissionA = new Permission("classname", "name", "actions");
         Permission permissionB = new Permission("classname", "name", "actions");
-        assertSame(permissionA, permissionA);
+        assertEquals(permissionA, permissionB);
         assertEquals(permissionA.getClassName(), permissionB.getClassName());
         assertEquals(permissionA.getName(), permissionB.getName());
         assertEquals(permissionA.getActions(), permissionB.getActions());
diff --git a/core/api/src/test/java/org/onosproject/store/service/DocumentPathTest.java b/core/api/src/test/java/org/onosproject/store/service/DocumentPathTest.java
index c0137c8..19c34bd 100644
--- a/core/api/src/test/java/org/onosproject/store/service/DocumentPathTest.java
+++ b/core/api/src/test/java/org/onosproject/store/service/DocumentPathTest.java
@@ -73,6 +73,7 @@
         DocumentPath path1 = exceptions("node|name", parentPath);
     }
 
+    @SuppressWarnings("SelfComparison")
     @Test
     public void comparePaths() {
         DocumentPath one = path("root");
diff --git a/core/api/src/test/java/org/onosproject/store/service/TestEventuallyConsistentMap.java b/core/api/src/test/java/org/onosproject/store/service/TestEventuallyConsistentMap.java
index 4a8dc47..280cffb 100644
--- a/core/api/src/test/java/org/onosproject/store/service/TestEventuallyConsistentMap.java
+++ b/core/api/src/test/java/org/onosproject/store/service/TestEventuallyConsistentMap.java
@@ -86,6 +86,7 @@
         return map.get(key);
     }
 
+    @SuppressWarnings("ReturnValueIgnored")
     @Override
     public void put(K key, V value) {
         map.put(key, value);
diff --git a/core/api/src/test/java/org/onosproject/store/service/WallClockTimestampTest.java b/core/api/src/test/java/org/onosproject/store/service/WallClockTimestampTest.java
index 3f02fef..8ea04fd 100644
--- a/core/api/src/test/java/org/onosproject/store/service/WallClockTimestampTest.java
+++ b/core/api/src/test/java/org/onosproject/store/service/WallClockTimestampTest.java
@@ -30,6 +30,7 @@
  */
 public class WallClockTimestampTest {
 
+    @SuppressWarnings("SelfComparison")
     @Test
     public final void testBasic() throws InterruptedException {
         WallClockTimestamp ts1 = new WallClockTimestamp();